Chemistry Forum

Hey, I'm trying to draw the mechanism for the catalytic hydrogenation of a NO₂ group with Pd/C as a catalyst. I've looked at several articles (mostly "Insights into the mechanism of nitrobenzene reduction to aniline over Pd catalyst and the significance of the adsorption of phenyl group on kinetics" and "Studying the Mechanisms of Nitro Compounds Reduction (A-Review)") but they show slightly different paths to how NO₂ turns into NH₂. I drew the mechanism, but I'm not sure it is correct, could anyone give it a look and let me know if there's something wrong with it?

Note: I'm not sure if it's okay, but I'm assuming the hydrogen atoms that are on the surface of the Pd are able to be taken by other atoms as either protons (H+) or hydrides.

I think that there’s a problem with charge in the first step.
How can a neutral compound become negative after getting a proton?
If H is not a proton but a hydride, how can a negative oxygen attack a negative hydride?

Do you think it would be better if in the first step the oxygen took the proton, but the other oxygen did not give its pi electrons to the positive nitrogen? That way the molecule in the second step would stay positive (due to the nitrogen's charge). The only thing is that if in the second step the oxygen with the double bond gives its pi electrons to the positive nitrogen, then in the third step the molecule would be negative and that isn't possible, is it? That a molecule goes from negative to positive charge all of a sudden, I mean.

After the oxygen gives its pi electron to nitrogen, the positive charge moves to oxygen and this molecule is still positive.

God, that's true, I don't know how that slipped my mind.

Thank you so much for your help!